1. Field of the Invention
This invention relates to liquid handling processes and apparatus. More particularly, this invention relates to new methods and apparatus for distributing the flow of liquid from a spray device.
2. Description of the Related Art
Fluidic inserts or oscillators are well known for their ability to provide a wide range of distinctive liquid sprays. The distinctiveness of these sprays is due to the fact that they are characterized by being oscillatory in nature, as compared to the relatively steady state flows that are emitted from standard spray nozzles.
FIG. 1 from U.S. Pat. No. 4,052,002 (Stouffer & Bray) demonstrates the oscillatory nature of the spray from a typical fluidic oscillator. It shows what can be considered to be the essentially temporally varying, two-dimensional, planar flow pattern (i.e., in the x-y plane of the oscillator, and assuming that the width of the oscillator in the z-direction is large in comparison to its throat or outlet dimension) of a liquid jet or spray that issues from the oscillator into a surrounding gaseous environment and breaks into droplets which are distributed transversely (i.e., in the y-direction) to the jet's generally x-direction of flow. Such spray patterns may be described by the definable characteristics of their droplets (e.g., the volume flow rate of the spray, the spray's area of coverage, the spatial distribution of droplets in planes perpendicular to the direction of flow of the spray and at various distances in front of the oscillator's outlet, the average droplet velocities, the average size of the droplets, and the frequency at which the droplets impact on an obstacle in the path of the spray).
A fluidic oscillator or insert is generally thought of as a thin, rectangular member that is molded or fabricated from plastic and has an especially-designed, uniform depth, liquid flow channel fabricated into either its broader top or bottom surface, and sometimes both (assuming that this fluidic insert is of the standard type that is to be inserted into the cavity of a housing whose inner walls are configured to form a liquid-tight seal around the insert and form an outside wall for the insert's boundary surface/s which contain the especially designed flow channels). See FIG. 2. Pressurized liquid enters such an insert and is sprayed from it.
Although it is more practical from a manufacturing standpoint to construct these inserts as thin rectangular members with flow channels in their top or bottom surfaces, it should be recognized that they can be constructed so that their liquid flow channels are placed practically anywhere (e.g., on a plane that passes though the member's center) within the member's body; in such instances the insert would have a clearly defined channel inlet and outlet.
Additionally, it should be recognized that these flow channels need not be of a uniform depth. For example, see U.S. Pat. No. 4,463,904 (Bray), U.S. Pat. No. 4,645,126 (Bray) and RE38,013 (Stouffer) for fluidic oscillators in which the bottom surfaces of these channels are discretely and uniformly sloped so as to impact the ways in which the sprays from these oscillators spread as the move away from the oscillator's outlet.
There are many well known designs of fluidic circuits that are suitable for use with such fluidic inserts. Many of these have some common features, including: (a) at least one power nozzle configured to accelerate the movement of the liquid that flows under pressure through the insert, (b) an interaction chamber through which the liquid flows and in which the flow phenomena is initiated that will eventually lead to the spray from the insert being of an oscillating nature, (c) an liquid inlet, (d) a pathway that connects the inlet and the power nozzle/s, and (e) an outlet or throat from which the liquid sprays from the insert.
Examples of fluidic circuits may be found in many patents, including U.S. Pat. No. 3,185,166 (Horton & Bowles), U.S. Pat. No. 3,563,462 (Bauer), U.S. Pat. No. 4,052,002 (Stouffer & Bray), U.S. Pat. No. 4,151,955 (Stouffer), U.S. Pat. No. 4,157,161 (Bauer), U.S. Pat. No. 4,231,519 (Stouffer), which was reissued as RE 33,158, U.S. Pat. No. 4,508,267 (Stouffer), U.S. Pat. No. 5,035,361 (Stouffer), U.S. Pat. No. 5,213,269 (Srinath), U.S. Pat. No. 5,971,301 (Stouffer), U.S. Pat. No. 6,186,409 (Srinath) and U.S. Pat. No. 6,253,782 (Raghu).
A key performance factor in many industrial applications for assorted spray devices, including fluidic oscillators, is the size of the area that the sprays from such devices can cover with liquid droplets—or alternatively, the lateral rate of spread of the fluid droplets as they proceed downstream. The degree of uniformity in the spatial distribution of these droplets can also be very important.
FIG. 3 shows the coordinate system which is used herein to describe how the spray from a fluidic oscillator spreads as it flows downstream from its origin at the oscillator's outlet. The centerline of the jet or spray is assumed to be in the x-direction and it exhibits both a lateral-horizontal spread in the x-y plane (referred to as the “width” of the spray and due primarily to the unique flow phenomena occurring within the insert that yields an essentially horizontally oscillating spray as shown in FIG. 1) which is defined by a horizontal fan angle, φ, and a lateral-vertical spread in the x-z plane (referred to as the “thickness” or “throw” of the spray) which is defined by a vertical spread angle, θ.
As one considers how to increase the lateral rate of spread of these liquid droplets and size of the area that they can cover, there is some prior art which is pertinent to this issue. For example, U.S. Pat. No. 4,151,955 (Stouffer), for what has come to be known as an “island” oscillator, discloses how one may cause the initial flow from a fluidic oscillator to take the form of a “sheet of liquid” or “sheet jet” that can be oscillated. This initial shape in the form of a sheet of liquid differs greatly from what normally is assumed to be the initially form of the flow from a fluidic oscillator—i.e., an essentially flat (i.e., very little thickness) but wide (i.e., large horizontal fan angle, φ) jet or spray of liquid droplets. See FIG. 4 from U.S. Pat. No. 4,151,955 for an illustration of the flapping of such a sheet and how this impacts the area wetted by such a spray.
Using the coordinate system shown in FIG. 3, the flow pattern shown in FIG. 4 can be described as an initial flow from the oscillator in the shape of a flat sheet that lies in the x-y plane. The flow phenomena inside the oscillator causes this sheet to be non-uniformly oscillated in this x-y plane such that its ends flap up and down in the z-direction which causes the sheet to wet an area having dimensions which are denoted in FIG. 4 as “H×S.” Thus, we have a somewhat rectangular area being wetted, rather than the relatively thin, wetted strip associated with the flow pattern shown in FIG. 1.
U.S. Pat. No. 4,151,955 reveals that this “rectangular area” rather than “strip” wetting phenomena is achieved by controlling how the flow oscillator's sidewalls or boundaries are contoured downstream of a fluidic oscillator's throat. FIGS. 5-7 from U.S. Pat. No. 4,151,955 show various configurations of what is referred to as an “island” oscillator. FIG. 5 illustrates that such an oscillator, which is distinguished, in part, by an expansion section downstream of its throat, which is identified by 35, 36 in FIG. 5, can be forced to yield an initial “sheet” jet if the extent of this section does not extend out beyond the dashed line 40. Locating the island (33) closer to the oscillator's outlet (34) is also reported to promote the formation of such a “sheet” jet.
FIG. 6 shows an island oscillator which has a section (identified by its sidewalls 101, 102 in FIG. 6) downstream of its throat (identified by 96, 97 in FIG. 6) in which the depth of this section has been reduced from what it was in the oscillator's oscillation chamber (93). See the cross-sectional view of this oscillator shown in FIG. 7. This change in this oscillator's configuration is also reported to promote the formation of a “sheet” rather than a “round” jet.
As fluidic oscillators have continued to be used in more types of applications, the opportunity has arisen to re-examine and improve upon their design, especially changing the geometry of their exits or outlets and the use of structures downstream of an oscillator's throat, as a way to improve upon the spreading characteristics of the sprays they emit. The results of our research in this area and the inventions that have come from our work are described herein.
3. Objects and Advantages
There has been summarized above, rather broadly, the prior art that is related to the present invention in order that the context of the present invention may be better understood and appreciated. In this regard, it is instructive to also consider the objects and advantages of the present invention.
It is an object of the present invention to provide the design for a new type of fluidic circuit that yields liquid sprays that are characterized by having enhanced thicknesses (i.e., the vertical rate of spread of such a spray's droplets is considerably greater than those of the usual “flat” sprays emitted by a wide range of fluidic circuits).
It is another object of the present invention to provide improvements in the design of the typical “island oscillator” so as to enable it to yield liquid sprays that are characterized by having enhanced thicknesses (i.e., the vertical rate of spread of such a spray's droplets is considerably greater than those of the usual “flat” sprays emitted by a wide range of fluidic circuits).
It is an object of the present invention to provide a liquid spray device that can enhance the rate of spread of the droplets that flow from such a spray device.
It is another object of the present invention to provide a liquid spray device that is especially well suited for cooling tower applications.
It is an object of the present invention to provide a clog-free, liquid spray device that is especially well suited for cooling tower applications.
It is a further object of the present invention to provide a liquid spray device that will provide clog-free performance in cooling tower applications while also providing equivalent or better cooling performance.
It is another object of the present invention to provide a liquid spray device that is especially well suited for cooling tower applications over a wide range of operating pressures (e.g., 1-5 psi) and flow rates (e.g., 10-90 gpm).
It is a still further object of the present invention to provide a liquid spray device that can uniformly spread liquid droplets over relatively large areas (4-8 sq. feet) located in close proximity (10-12 inches) to the device while operating at relatively large flow rates (25-85 gpm) and line pressures in the range of 0.5 to 6 psi.
It is an object of the present invention to provide a liquid spray device that can provide both horizontal and vertical rates of spread in the range of 70-120 degrees and 100-160 degrees, respectively, for the droplets that flow from such a spray device.
These and other objects and advantages of the present invention will become readily apparent as the invention is better understood by reference to the accompanying summary, drawings and the detailed description that follows.